Fully Digital Pulse Oximeter Cosine Wave Driven Generate two PPG AMs and AM Synchronous Detector with Single Microcontroller

In this article, an embedded microcontroller ESP32 implement to be a pulse oximeter is proposed. The almost overall system operates on a microcontroller except for the analog front-end trans-impedance amplifier. The system works by generating two different frequency cosines with cosine function and converting them to be analog cosine signals to drive IR and Red-light sources. The two PPG AM signals are summed in FDM form at the output of the light detector, and it is amplified and converted to be digital signal by the microcontroller after that the digital signal as mentioned above is selected by two digital BPFs with different center frequencies and two PPG AMs are obtained. Two PPG AMs have been demodulated with AM synchronous detector therefore the PPG IR and PPG RED are obtained. They are employed to estimate oxygen saturated and display on OLED along with mobile devices android OS by Bluetooth communication channel. The experiment results show that the proposed system can well operate and have accuracy and precision are 98.1261% and 0.9031, respectively.